The title pretty much sums it up. It seems plausible to me that an assumption that a question about a book is liable to contain spoilers is enough reason to not use spoiler markup. I wanted to ask and be sure, though.
Honestly, I'm a big fan of M&TV's policy:
No Spoilers in Titles
Most answers will contain spoilers to someone. There's no way to draw a line that will make everyone happy.
If the OP is asking for advice about a book they have not read, answers should be considerate of this and consider putting major plot points in spoiler markup.
I don't want to have a bunch of questions and answers that only look like:
text text text text text text
and then they
text text text text text text
I'm sorry but this is useless to everyone involved.
I would avoid excessive spoiler markup. Most of the question about a book will naturally talk about its content and story and thus potentially contain spoilers (not to speak of the subjective notion of what a spoiler actually is). Not only would trying to consistently police them and add spoiler blocks be a maintenance mess, it also often makes the questions downright incomprehensible and a formatting mess.
I would thus propose that spoiler block usage be kept to a minimum and the question (or answer) should definitely make sense even when ignoring the spoiler blocks. The only case where spoiler blocks seem reasonable would be when talking about spoilers from works that are not apparent from the question itself (e.g. books the questions didn't explicitly ask about).
Where I would, however, strongly avoid spoilers is the question titles, since they are apparent to all users browsing the front-page and before looking into a question you need to know if it potentially spoils you or not.
While not necessarily important for the policy on this site, it is worth mentioning that this is the currently practiced spoiler policy on Movies & TV. For the relevant meta questions see this and this.
It is in the nature of this site that both questions and answers may contain spoilers. It is sometimes possible to write submissions in a way that minimises spoilers, but sometimes there is no way around it. My two arguments against spoiler markup are the following:
- It is reasonable to assume that readers are intelligent enough to know that content on this site can contain spoilers.
- At the time of writing, spoilers are inaccessible to keyboard users.
I would even go a step further and state that spoilers should not be visible in the preview.
My best guess is the main site preview shows around 200 characters and the search preview shows around 400 characters. However, search preview also shows the relevant sections of answers that contain the search terms, which means that a spoiler can be revealed through search preview.
I suppose what would be nice is a spoiler markup reveal option at the top of the page which allows disabling all of the spoiler blocks on a given page to improve readability for those who are not concerned with spoilers, but that is likely not an available option, so something else?
Just to point out how lame the policy is, here is a spoiler. We can see the striking effectiveness of not placing the spoiler in the title, but still having it visible in the preview: